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Mathematical Treasure: Henrion's Use of the Proportional Compass

Author(s):

Frank J. Swetz (Pennsylvania State University)

This woodcut illustration appeared in Denis Henrion’s L’Usage du compas de proportion (Use of the Proportional Compass),first published in 1618. The tool in the man's hands is a proportional compass, or sector. Henrion's book was popular: WorldCat reports "11 editions published between 1631 and 1685 in French." Denis Henrion and Pierre Hérigone were pseudonyms of Baron Clément Cyriaque de Mangin (1580-1643).

The image above appears on the website of the Computer History Museum, where it is credited to Erwin Tomash. Tomash (1921-2012) founded the Charles Babbage Institute, dedicated to the history of information technology and housed at the University of Minnesota. Much of his personal library now makes up the Erwin Tomash Library on the History of Computing at the Charles Babbage Institute.

Henrion was the author of several different manuals on the use of mathematical instruments. In 1618, he published L' usage du compas de proportion (Use of the Proportional Compass). The title page below comes from the expanded fourth edition in 1631.